Figure 5-14. Trombicula mite larva.
Figure 5-15. Freeliving adult mite.
5-46. SCRUB TYPHUS
a. General. Scrub typhus (mite-borne typhus, tsutsugamushi disease) is a
febrile infectious disease caused by Rickettsia tsutsugamushi and is transmitted to man
by the bite of infected larvae of Trombiculid mites.
b. Signs/Symptoms.
(1) Clinical course. The clinical course resembles that of other typhus-like
disease.
A primary lesion (eschar) occurs at the site of attachment of the mite
4 or 5 days after attachment.
Onset of the acute febrile stage is from 6 to 21 days, usually 10 to
12, after attachment of the chigger.
In the absence of specific therapy, fever persists for about 2 weeks.
(2) Immunity.
In the general population, from 1 % to 40% of untreated cases
terminate fatally.
Scrub typhus can recur in the same individual, since one attack
confers long-term immunity only to the specific strain of R. tsutsugamushi that caused
the initial attack.
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